The development of humanoid robots has been in progress.
Such humanoid robots are expected to perform sophisticated actions such as touching with a human, autonomously avoiding an obstacle, and grasping and transporting an object.
Since sensing of touch is necessary for such actions, a technique for providing a tactile sensor on a hand portion of a robot or the entire body surface of a robot has been studied in recent years (for example, Patent Literatures 1 and 2).
Examples of the actions expected to be performed by a robot include an action of grasping an object.
FIG. 18 is a diagram showing a state where a robot 10 lifts an object 13 with a hand portion 12.
Referring to FIG. 18, the hand portion 12 of the robot 10 is provided with a tactile sensor unit 14 that detects a contact with the object 13.
The robot 10 grasps and lifts the object 13 with an appropriate force by a feedback control based on a contact force detected by the tactile sensor unit 14.
Forces acting between the hand portion 12 of the robot 10 and the object 13 include a normal stress acting perpendicularly to a gripping surface of the hand portion 12 of the robot 10, and a shearing force (a shearing stress, a tangential stress) acting in the tangential direction along the surface of the hand portion 12 of the robot 10.
In the case of detecting a normal stress, an existing force detection sensor for detecting a perpendicularly acting force may be used.
On the other hand, it is not always easy to detect a shearing force.
In this regard, Patent Literature 1 discloses the sensor unit 14 that detects a shearing force from an object as shown in FIG. 19.
The sensor unit 14 disclosed in Patent Literature 1 has a configuration as described below.
The sensor unit 14 includes a deformable member 31 which is to be deformed by a shearing force received from an object, and a strain sensor 32 buried in the deformable member 31.
The strain sensor 32 includes flat plates 32a standing perpendicularly as cantilevers, and strain gauges 32b attached to the respective flat plates 32a. 
When a shearing force (a tangential stress) acts on the surface of the deformable member 31, the deformable member 31 strains.
Along with this strain, the cantilevers 32a also strain.
The strain gauges 32b detect the amount of deformation of the cantilevers 32a at this time, thereby detecting the shearing force acting on the surface of the deformable member 31.
As shown in FIG. 20, Patent Literature 2 discloses a tactile sensor device 20 having a configuration in which cantilevers 41, each of which stands erect from a base 16 through a hinge, are buried in an elastic body 42 made of silicon.
Indeed, the configuration in which the cantilevers standing erect are buried in the deformable member as disclosed in Patent Literatures 1 and 2 enables detection of a shearing force acting on the deformable member.